Bosch WTN85251GB/05 Condenser Dryer Error E90 - Page 1
Forum section: electronics / repair

author: Squarewave
author_rank: Frequent Contributor
timestamp: October 08, 2024, 10:24:54 pm
content: So my 4 year old dryer has started giving me the E90 code, after several attempts of starting. During the attempts, I can hear a relay clicking away. Some searching on the web brought up this threadhttps://www.eevblog.com/forum/repair/bosch-wtn83200gb-tumble-dryer-(condenser-non-heatpump-type)-e90-code-instantly/so I thought I'd start by taking a look at the board, which looks similar, so perhaps the same issue?I'll order some relays and give it a go. Rather than add to someone elses thread, I thought I'd make my own. Photos attached.

author: tom66
author_rank: Super Contributor
timestamp: October 09, 2024, 08:28:57 am
content: Per your PM.In my case, I bought these replacements from Rapid Electronics.https://www.rapidonline.com/catalogue/product/49-4255I am sure though if you find the pin dimensions, current and voltage ratings (especially pay attention to the coil rating) you can find an equivalent from other places. Relays don't come in that many shapes and many are pattern parts of each other.Also, be aware that other relays may be the cause of your fault, for all I know. I tested my relays to find the defective one.

author: Squarewave
author_rank: Frequent Contributor
timestamp: October 09, 2024, 10:59:23 am
content: Hi, thanks for the information. The mistake I'd made is put the board back into the drier without measuring the pin layout, thinking that I'd easily find a datasheet for the NF relays where I could match up a relay, but couldn't find one at all. Then from my usual suppliers (I've not used Rapid before) I put in 9VDC coils and there wasn't much to choose from.The four square relays are all the same size, but my problem is for 9v coils, is now finding the 16a ones in case I need to replace them all, but same issue with finding datasheets for those ones also. They're not the kind where you can pop the lid off and clean the contacts out! But the issue is most likely one of the 10amp ones. For the cost and whilst I have the board out, I'd intend to replace them all.

author: tom66
author_rank: Super Contributor
timestamp: October 09, 2024, 11:15:32 am
content: Interesting that your board has Hongfa relays everywhere mine didn't have them, so maybe it's not a Hongfa problem and just underrated/cheap relays. Yes, I'd replace then all having seen what happened to the contacts on two of mine. Mine is still going strong a year later and it gets weekly use, so we'll see if anything else fails.Edit - correct error

author: Squarewave
author_rank: Frequent Contributor
timestamp: October 09, 2024, 11:37:37 am
content: It's mad here, it's on once or twice a day, with the rain we've been having, it's an issue if it goes out of action! Luckily it's still working but you need to give it a few goes before it starts.

author: Squarewave
author_rank: Frequent Contributor
timestamp: October 09, 2024, 11:51:00 am
content: Did your replacement relay have the two pins close together or was it the usual lay out, so you just cut the one off not being used where there isn't a through hole on the board?

author: tom66
author_rank: Super Contributor
timestamp: October 09, 2024, 12:50:07 pm
content: I recall having to cut one pin off as the board was designed for a NO relay instead of NCNO. Just check the datasheet carefully.

author: Squarewave
author_rank: Frequent Contributor
timestamp: October 09, 2024, 01:26:53 pm
content: It sounds right, from memory looking at the back of the board it looked like 1 Form A with double pins, but a single pin should work fine and if I can't find a 1 Form A, then a 1 Form C with the unused pin cut off will work fine.

author: Squarewave
author_rank: Frequent Contributor
timestamp: October 09, 2024, 02:00:17 pm
content: So I think the two NF Forward 16A relays, this can be its replacement (with pin 4 chopped off in 1 Form C)https://www.mouser.co.uk/datasheet/2/307/en_g5le-3447037.pdfAnd for the 10A Hongfa, either the Finder which you linked to, or if I'm ordering from the same place, then this which I can get in 1 Form Ahttps://www.mouser.co.uk/datasheet/2/307/en_g5le-3447037.pdf