hello i have a 1987 blazer s10 i was driving home and the temp tool forever to get up there but when it got too 100f it still climbed to 110 then kinda hovered. when i turned my truck off the blower motor said no and stayed on. the only way to stop it is to unplug it. what do you think my problems are? any help is thanked alot.

 

Does it stay on only on high or any speed. I've been all through the blower issue with my 94 and you need the wiring diagram to understand how it works. Not sure if your 87 is the same but I doubt it's much different. Sounds like you probably have a blower relay issue, but a little more information would help.

 

gimpy blazer, it stays on when on all speeds. even if i turn it off on the switch it is still on one time 2 days ago it happened and i kinda just hit the blower motor casing and it stopped but now it wont.

 

It sounds like you either have wires crossed somewhere or your HVAC control head has gone bad inside. Have you tried disconnecting the HVAC control head electrical connections?

 

i can try but what would i check for?

 

Start by completely disconnecting everything from the dashboard controls for the HVAC system.

 

Quick question. Does the blower run at different speeds or just one?
Here is a brief overview on how this is wired. Again, I'm looking at a 94 factory diagram but have cross rerferenced it to a Chilton 87 diagram. They work (wired) the same. After looking at your problem again (blower stays on at all times) the only source of power when the truck is off would be from the red wire at the blower relay in the engine compartment. This wire comes from the ""hot at all times" junction block and powers the blower motor only in "Hi". When you turn the blower switch to Hi, that energizes the blower relay and shifts the power source away from the resistor directly from the junction block to the motor. Try these checks.
1) With switch in "Hi" see if you have power to the Orange wire at the relay in the engine compartment. You should. Any other switch position you should not.
2) Pull the 25 amp Htr/AC fuse under the dash. Does the blower still run? It shouldn't. What you have done is killed power to the relay. If it still runs, then it indeed is getting power from the red wire from the junction block on the firewall and I suspect that your relay may be fried inside and the motor is getting continuous power from the junction block.
Hope this helps. Relays are cheap. Please let us know how you made out one way or another. There is other stuff you can try but the switch being bad is a possibility too. Really need to know exactly what it's doing in what switch position and how fast it's runnung. You don't need a lot of high dollar equipment. A simple test light or cheap meter will work fine. I didn't want to try to explain the whole system to you here. Just that the blower motor gets it juice from two completely different power sources in your truck. If this doesn't work, then we'll go from there. You wouldn't believe all the screwed up stuff that was on mine. Works as advertised now though.

 

wow thats alot of help thanks ill take a look tomorrow on my day off and let you all know how my findings went

 

hello i used your diag tips and they really helped it need just a relay. and my problem was solved thanks for all the extra above and beyond help

 

Glad to help. Still don't know why beating on the dash helped. You might have another issue but as my dear ole dad always says "Don't fight success". Keep Blazin'